DOCSLIB.ORG

Multiplicity Among Solar-Type Stars IV. the CORAVEL Radial Velocities And

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Multiplicity Among Solar-Type Stars IV. the CORAVEL Radial Velocities And Astronomy & Astrophysics manuscript no. Halbwachs c ESO 2018 August 15, 2018 Multiplicity among solar-type stars IV. The CORAVEL radial velocities and the spectroscopic orbits of nearby K dwarfs⋆ J.-L. Halbwachs1, M. Mayor2, and S. Udry2 1 Université de Strasbourg, CNRS, Observatoire Astronomique de Strasbourg, UMR 7550, 11, rue de l’Université, F–67 000 Stras- bourg, France e-mail: [email protected] 2 Observatoire Astronomique de l’Université de Genève, 51, chemin des Maillettes, CH–1290 Sauverny, Switzerland Received 7 May 2018; accepted 2 August 2018 ABSTRACT Context. The statistical properties of binary stars are clues for understanding their formation process. A radial velocity survey was carried on amongst nearby G-type stars and the results were published in 1991. Aims. The survey of radial velocity measurements was extended towards K-type stars. Methods. A sample of 261 K-type stars was observed with the spectrovelocimeter CORAVEL (COrrelation RAdial VELocities). Those stars with a variable radial velocity were detected on the basis of the P(χ2) test. The orbital elements of the spectroscopic binaries were then derived. Results. The statistical properties of binary stars were derived from these observations and published in 2003. We present the cata- logue of the radial velocity measurements obtained with CORAVEL for all the K stars of the survey and the orbital elements derived for 34 spectroscopic systems. In addition, the catalogue contains eight G-type spectroscopic binaries that have received additional measurements since 1991 and for which the orbital elements are revised or derived for the first time. Key words. solar neighbourhood – binaries: spectroscopic – Stars: solar–type – Stars: late–type 1. Introduction that gave rise to Paper III. It will give the orbits we have discov- ered all the visibility they deserve, so that they are henceforth The spectrovelocimeter CORAVEL (COrrelation RAdial VE- taken into account in statistical studies, such as that of Raghavan Locities, Baranne et al. 1979) was installed on the Swiss 1-m et al. (2010). Moreover, they will be available for the valida- telescope at the Observatory of Haute-Provence (OHP) from the tion of the spectroscopic orbits derived from the Radial Veloc- late 1970s until its decommissioning in 2000. Amongst other ity Spectrometer of the Gaia satellite (Gaia Collaboration et al. programmes, it provided the radial-velocity (RV) measurements 2016). The CORAVEL programme is presented in Sect. 2, the exploited in two statistical studies of binarity among the stars in RV catalogue is in Sect. 3, and the spectroscopic orbital elements the solar neighbourhood: the study of solar–type stars until G8, are in Sect. 4. Section 5 is the conclusion. and its extension towards the K-type stars. A series of articles has been devoted to these programmes. The first (Duquennoy et al. 1991, Paper I hereafter) presented the radial-velocity measure- 2. The CORAVEL survey of nearby K-type stars ments of the sample of F-G type stars; these data led to the or- bital elements of several spectroscopic binaries (SBs), and to the The CORAVEL survey for nearby SBs was initiated in the early statistical properties of solar-type binaries (Duquennoy & Mayor 1980s, although some stars (especially among the F–G types) arXiv:1808.04605v1 [astro-ph.SR] 14 Aug 2018 1991, DM91 hereafter). Later, Halbwachs et al. (2003, Paper III had been measured before. The stars were taken from the second hereafter) extended the statistical investigations to the K-type bi- edition of the “Catalogue of Nearby Stars” (CNS Gliese 1969) naries with periods shorter than ten years, again on the basis of and from its supplement (Gliese & Jahreiss 1979). The stars dis- CORAVEL observations. This paper presented the parameters carded from the preliminary third version of the CNS (CNS3 relevant for statistics, namely the periods, the semi-amplitudes, Gliese & Jahreiss 1991) were kept in the observing runs. All the mass ratios, and the orbital eccentricities of the spectroscopic stars were observed with CORAVEL from the Haute–Provence binaries, excluding the other orbital elements. The long period Observatory. Due to the location of the instrument and to its − ◦ K-type binaries were eventually studied by Eggenberger et al. characteristics, only the stars as late as F7 and northern to 15 (2004). in declination were observed. Some stars with declination below − ◦ The present paper completes the series by presenting the ra- 15 were observed, but they were not taken into account in Pa- dial velocity measurements and the full set of orbital elements per III. The programme was split according to the spectral types of the stars: the search for SBs amongst 288 F–G stars ended in ⋆ Based on photoelectric radial-velocity measurements collected at December 1989, but the detection of SBs amongst the K–type Haute-Provence Observatory. stars was intensively performed until July 1993. After this date, Article number, page 1 of 18 A&A proofs: manuscript no. Halbwachs the SBs were observed until 2000; at the same time, the RV of 40 a few stars were still measured in order to confirm that it was constant. 3. Radial-velocity catalogues 3.1. CORAVEL individual measurements n 20 The catalogue of the RV measurements provides 5413 mea- surements for 269 stars: 261 K–type stars and eight stars from the sample of DM91. These eight G–type stars were already in Paper I or another paper quoted in DM91, but they fulfil two conditions: they received enough additional RV measurements between 1991 and 2000 to significantly improve their spectro- scopic orbit, and this new CORAVEL orbit was not published 0 elsewhere. Moreover, the reduction of the CORAVEL observa- 0 5 10 15 20 tions was slightly improved, and the RV measurements are not N1 exactly the same as in Paper I. The format of the catalogue is presented in Table 1. Each Fig. 1. Histogram of the number of observations. The shaded area refers to the stars that were not considered as variable and the white area to the record consists in the following data: spectroscopic binaries. The last bin represents all the stars with at least – 21 observations; for the spectroscopic binaries, the count in this bin is The number of the star in the CNS, followed by a letter des- 72. ignating the component, if any. – The epoch of the observation, given as a date with the year, the month, and the day, and also as barycentric Julian Day – The B−V colour index used to derive the CORAVEL RVs of (BJD). the star. For the eight stars from the G–type sample, B − V = – The RV, in km s−1. 0.63 was assumed. – The uncertainty of the RV. – The mean RV, RV. When the star is a binary with known – The index of component (“1” for the primary, “2” for the orbital elements, the RV of the barycentre is provided, as it secondary). is in Table A.2. – A flag “R” indicates the measurement was discarded from – ǫ is the uncertainty of RV. the calculation of the orbital elements. – σRV is the standard deviation of the RV measurements. – E/I is the ratio of external to internal errors. The records are sorted by stars (from the smallest to the – P(χ2) is the probability to obtain the χ2 of the RVs of the largest right ascension), and then by observation epochs. star, assuming that the RV is constant in reality. – N1 is the number of observations of the star. 3.2. Elodie individual measurements – Ntot is the number of RV measurements of the primary and of the secondary components. The CORAVEL observations were not sufficiently accurate to – ∆T is the time span of the observation. derive valuable SB orbital elements for two stars of the sam- – The spectroscopic status is “CST” (ConStanT) when P(χ2) ple, GJ 1069 and GJ 554. The latter of these two stars is even a is more than 1%. Otherwise, it is SB1, or SB2 when the RV constant velocity star when only the CORAVEL RVs are consid- of the secondary component was measured. An “O” indi- ered. Fortunately, RV measurements were performed thanks to cates that the orbital elements were derived, as explained in the spectrograph Elodie of the 193 cm telescope at the Haute- Sect. 4 hereafter. One star, GJ 554, has a constant CORAVEL Provence Observatory, and they are provided by the Elodie RV, but an SB orbit derived by adding Elodie RV; this star archive (http://atlas.obs-hp.fr/elodie/). Fifteen Elodie RVs of GJ is flagged “CSTO”. The status of two stars (GJ 893.2B and 1069 and 58 RVs of GJ 554 are presented in a separate file, with GJ 907.1) is “?” since only one RV measurement was ob- a slightly different format due to their accuracy. The uncertain- tained; these stars have both declinations around −10 ◦, and ties of the Elodie RVs were estimated as explained in Sect. 4.1. are too faint to be easily observable.However, they were only Sample records are presented at the end of Table 1. in the so-called “extended sample” of Paper III, and they were not relevant in the statistical investigations. – A flag indicates that the SB orbital elements of the star are in 3.3. The mean RV and the detection of SBs Table A.2, “*” when they are derived for the first time, and The RV measurements were used to derive statistical informa- “+” otherwise. The velocity curves of the flagged stars are in tion to decide whether a star is binary or not. These data are Figs. 3, 4, and 5. provided in Table A.1. The content is the following: The efficiency of the detection of the SBs depends on the time spans of the RV survey and on the numbers of RV measure- – The identification of the star is the CNS number (GJ), as in ments per star.
Load more

Recommended publications
  • Catalog of Nearby Exoplanets
    Catalog of Nearby Exoplanets1 R. P. Butler2, J. T. Wright3, G. W. Marcy3,4, D. A Fischer3,4, S. S. Vogt5, C. G. Tinney6, H. R. A. Jones7, B. D. Carter8, J. A. Johnson3, C. McCarthy2,4, A. J. Penny9,10 ABSTRACT We present a catalog of nearby exoplanets. It contains the 172 known low- mass companions with orbits established through radial velocity and transit mea- surements around stars within 200 pc. We include 5 previously unpublished exo- planets orbiting the stars HD 11964, HD 66428, HD 99109, HD 107148, and HD 164922. We update orbits for 90 additional exoplanets including many whose orbits have not been revised since their announcement, and include radial ve- locity time series from the Lick, Keck, and Anglo-Australian Observatory planet searches. Both these new and previously published velocities are more precise here due to improvements in our data reduction pipeline, which we applied to archival spectra. We present a brief summary of the global properties of the known exoplanets, including their distributions of orbital semimajor axis, mini- mum mass, and orbital eccentricity. Subject headings: catalogs — stars: exoplanets — techniques: radial velocities 1Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the Uni- versity of California and the California Institute of Technology. The Keck Observatory was made possible by the generous financial support of the W. M. Keck Foundation. arXiv:astro-ph/0607493v1 21 Jul 2006 2Department of Terrestrial Magnetism, Carnegie Institute of Washington, 5241 Broad Branch Road NW, Washington, DC 20015-1305 3Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720-3411 4Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132 5UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 6Anglo-Australian Observatory, PO Box 296, Epping.
    [Show full text]
  • Naming the Extrasolar Planets
    Naming the extrasolar planets W. Lyra Max Planck Institute for Astronomy, K¨onigstuhl 17, 69177, Heidelberg, Germany [email protected] Abstract and OGLE-TR-182 b, which does not help educators convey the message that these planets are quite similar to Jupiter. Extrasolar planets are not named and are referred to only In stark contrast, the sentence“planet Apollo is a gas giant by their assigned scientific designation. The reason given like Jupiter” is heavily - yet invisibly - coated with Coper- by the IAU to not name the planets is that it is consid- nicanism. ered impractical as planets are expected to be common. I One reason given by the IAU for not considering naming advance some reasons as to why this logic is flawed, and sug- the extrasolar planets is that it is a task deemed impractical. gest names for the 403 extrasolar planet candidates known One source is quoted as having said “if planets are found to as of Oct 2009. The names follow a scheme of association occur very frequently in the Universe, a system of individual with the constellation that the host star pertains to, and names for planets might well rapidly be found equally im- therefore are mostly drawn from Roman-Greek mythology. practicable as it is for stars, as planet discoveries progress.” Other mythologies may also be used given that a suitable 1. This leads to a second argument. It is indeed impractical association is established. to name all stars. But some stars are named nonetheless. In fact, all other classes of astronomical bodies are named.
    [Show full text]
  • Exoplanet Detection Techniques
    Exoplanet Detection Techniques Debra A. Fischer1, Andrew W. Howard2, Greg P. Laughlin3, Bruce Macintosh4, Suvrath Mahadevan5;6, Johannes Sahlmann7, Jennifer C. Yee8 We are still in the early days of exoplanet discovery. Astronomers are beginning to model the atmospheres and interiors of exoplanets and have developed a deeper understanding of processes of planet formation and evolution. However, we have yet to map out the full complexity of multi-planet architectures or to detect Earth analogues around nearby stars. Reaching these ambitious goals will require further improvements in instru- mentation and new analysis tools. In this chapter, we provide an overview of five observational techniques that are currently employed in the detection of exoplanets: optical and IR Doppler measurements, transit pho- tometry, direct imaging, microlensing, and astrometry. We provide a basic description of how each of these techniques works and discuss forefront developments that will result in new discoveries. We also highlight the observational limitations and synergies of each method and their connections to future space missions. Subject headings: 1. Introduction tary; in practice, they are not generally applied to the same sample of stars, so our detection of exoplanet architectures Humans have long wondered whether other solar sys- has been piecemeal. The explored parameter space of ex- tems exist around the billions of stars in our galaxy. In the oplanet systems is a patchwork quilt that still has several past two decades, we have progressed from a sample of one missing squares. to a collection of hundreds of exoplanetary systems. Instead of an orderly solar nebula model, we now realize that chaos 2.
    [Show full text]
  • Exoplanetary Geophysics--An Emerging Discipline
    Invited Review for Treatise on Geophysics, 2nd Edition Exoplanetary Geophysics { An Emerging Discipline Gregory Laughlin UCO/Lick Observatory, University of California, Santa Cruz, Santa Cruz, CA 95064, USA Jack J. Lissauer NASA Ames Research Center, Planetary Systems Branch, Moffett Field, CA 94035, USA 1. Abstract Thousands of extrasolar planets have been discovered, and it is clear that the galactic planetary census draws on a diversity greatly exceeding that exhibited by the solar system's planets. We review significant landmarks in the chronology of extrasolar planet detection, and we give an overview of the varied observational techniques that are brought to bear. We then discuss the properties of the planetary distribution that is currently known, using the mass-period diagram as a guide to delineating hot Jupiters, eccentric giant planets, and a third, highly populous, category that we term \ungiants", planets having masses M < 30 M⊕ and orbital periods P < 100 d. We then move to a discussion of the bulk compositions of the extrasolar planets, with particular attention given to the distribution of planetary densities. We discuss the long-standing problem of radius anomalies among giant planets, as well as issues posed by the unexpectedly large range in sizes observed for planets with mass somewhat greater than Earth's. We discuss the use of transit observations to probe the atmospheres of extrasolar planets; various measurements taken during primary transit, secondary eclipse, and through the full orbital period, can give clues to the atmospheric compositions, structures and meteorologies. The extrasolar planet catalog, along with the details of our solar system and observations of star-forming regions and protoplanetary disks, arXiv:1501.05685v1 [astro-ph.EP] 22 Jan 2015 provide a backdrop for a discussion of planet formation in which we review the elements of the favored pictures for how the terrestrial and giant planets were assembled.
    [Show full text]
  • International Astronomical Union Commission G1 BIBLIOGRAPHY
    International Astronomical Union Commission G1 BIBLIOGRAPHY OF CLOSE BINARIES No. 108 Editor-in-Chief: W. Van Hamme Editors: R.H. Barb´a D.R. Faulkner P.G. Niarchos D. Nogami R.G. Samec C.D. Scarfe C.A. Tout M. Wolf M. Zejda Material published by March 15, 2019 BCB issues are available at the following URLs: http://ad.usno.navy.mil/wds/bsl/G1_bcb_page.html, http://faculty.fiu.edu/~vanhamme/IAU-BCB/. The bibliographical entries for Individual Stars and Collections of Data, as well as a few General entries, are categorized according to the following coding scheme. Data from archives or databases, or previously published, are identified with an asterisk. The observation codes in the first four groups may be followed by one of the following wavelength codes. g. γ-ray. i. infrared. m. microwave. o. optical r. radio u. ultraviolet x. x-ray 1. Photometric data a. CCD b. Photoelectric c. Photographic d. Visual 2. Spectroscopic data a. Radial velocities b. Spectral classification c. Line identification d. Spectrophotometry 3. Polarimetry a. Broad-band b. Spectropolarimetry 4. Astrometry a. Positions and proper motions b. Relative positions only c. Interferometry 5. Derived results a. Times of minima b. New or improved ephemeris, period variations c. Parameters derivable from light curves d. Elements derivable from velocity curves e. Absolute dimensions, masses f. Apsidal motion and structure constants g. Physical properties of stellar atmospheres h. Chemical abundances i. Accretion disks and accretion phenomena j. Mass loss and mass exchange k. Rotational velocities 6. Catalogues, discoveries, charts a. Catalogues b. Discoveries of new binaries and novae c.
    [Show full text]
  • Arxiv:2010.00015V3 [Hep-Ph] 26 Apr 2021 Galactic Halo Can Scatter with Exoplanets, Lose Energy, and Gles Are the Same Set of Planets, Without DM Heating
    MIT-CTP/5230 SLAC-PUB-17556 Exoplanets as Sub-GeV Dark Matter Detectors Rebecca K. Leane1, 2, ∗ and Juri Smirnov3, 4, y 1Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 2SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94039, USA 3Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, Columbus, OH 43210, USA 4Department of Physics, The Ohio State University, Columbus, OH 43210, USA (Dated: April 27, 2021) We present exoplanets as new targets to discover Dark Matter (DM). Throughout the Milky Way, DM can scatter, become captured, deposit annihilation energy, and increase the heat flow within exoplanets. We estimate upcoming infrared telescope sensitivity to this scenario, finding actionable discovery or exclusion searches. We find that DM with masses above about an MeV can be probed with exoplanets, with DM-proton and DM-electron scattering cross sections down to about 10−37cm2, stronger than existing limits by up to six orders of magnitude. Supporting evidence of a DM origin can be identified through DM-induced exoplanet heating correlated with Galactic position, and hence DM density. This provides new motivation to measure the temperature of the billions of brown dwarfs, rogue planets, and gas giants peppered throughout our Galaxy. Introduction{Are we alone in the Universe? This ques- Exoplanet Temperatures tion has driven wide-reaching interest in discovering a 104 planet like our own. Regardless of whether or not we ever find alien life, the scientific advances from finding DM Heating and understanding other planets will be enormous. From a particle physics perspective, new celestial bodies pro- vide a vast playground to discover new physics.
    [Show full text]
  • Orders of Magnitude (Length) - Wikipedia
    03/08/2018 Orders of magnitude (length) - Wikipedia Orders of magnitude (length) The following are examples of orders of magnitude for different lengths. Contents Overview Detailed list Subatomic Atomic to cellular Cellular to human scale Human to astronomical scale Astronomical less than 10 yoctometres 10 yoctometres 100 yoctometres 1 zeptometre 10 zeptometres 100 zeptometres 1 attometre 10 attometres 100 attometres 1 femtometre 10 femtometres 100 femtometres 1 picometre 10 picometres 100 picometres 1 nanometre 10 nanometres 100 nanometres 1 micrometre 10 micrometres 100 micrometres 1 millimetre 1 centimetre 1 decimetre Conversions Wavelengths Human-defined scales and structures Nature Astronomical 1 metre Conversions https://en.wikipedia.org/wiki/Orders_of_magnitude_(length) 1/44 03/08/2018 Orders of magnitude (length) - Wikipedia Human-defined scales and structures Sports Nature Astronomical 1 decametre Conversions Human-defined scales and structures Sports Nature Astronomical 1 hectometre Conversions Human-defined scales and structures Sports Nature Astronomical 1 kilometre Conversions Human-defined scales and structures Geographical Astronomical 10 kilometres Conversions Sports Human-defined scales and structures Geographical Astronomical 100 kilometres Conversions Human-defined scales and structures Geographical Astronomical 1 megametre Conversions Human-defined scales and structures Sports Geographical Astronomical 10 megametres Conversions Human-defined scales and structures Geographical Astronomical 100 megametres 1 gigametre
    [Show full text]
  • Stellar Activity Mimics Planetary Signal in the Habitable Zone of Gliese 832
    UNIVERSIDAD DE CONCEPCIÓN FACULTAD DE CIENCIAS FÍSICAS Y MATEMÁTICAS MAGÍSTER EN CIENCIAS CON MENCIÓN EN FÍSICA Gliese 832c: ¿Actividad Estelar o Exoplaneta? Gliese 832c: Stellar Activity or Exoplanet? Profesores: Dr. Nicola Astudillo Defru Dr. Ronald Mennickent Cid Dr. Sandro Villanova Tesis para ser presentada a la Dirección de Postgrado de la Universidad de Concepción PAULA GORRINI HUAIQUIMILLA CONCEPCION - CHILE 2020 “... we cannot accept anything as granted, beyond the first mathematical formulae. Question everything else. ” Maria Mitchell iii UNIVERSIDAD DE CONCEPCIÓN Abstract Facultad de Ciencias Físicas y Matemáticas Departmento de Astronomía MSc. Stellar activity mimics planetary signal in the habitable zone of Gliese 832 by Paula GORRINI Exoplanets are planets located outside our Solar System. The search of these objects have grown during the years due to the scientific interest and to the advances on astronomical instrumentation. There are many methods used to detect exoplanets, where one of the most efficient is the radial velocity (RV) method. But this technique accounts false positives as stellar activity can produce RV variation with an ampli- tude of the same order of the one induced by a planetary companion. In this thesis, we study Gliese 832, an M dwarf located 4.96 pc away from us. Two planets orbiting this star were found independently by the RV method: a gas-giant planet in a wide orbit, and a super Earth or mini-Neptune located within the stellar habitable zone. However, the orbital period of this latter planet is close to the stellar rotation period, casting doubts on the planetary origin of this RV signal.
    [Show full text]
  • Hubble Space Telescope – Fine Guidance Sensors
    National Aeronautics and Space Administration Hubble Space Telescope – Fine Guidance Sensors For the Hubble Space Telescope to perform as Overview the premier astronomical observatory of our time, The FGSs provide pointing information for the the telescope must precisely point and stabilize its spacecraft and can also function as a scientific gaze on the sky so that its scientific instruments instrument to perform celestial measurements. can collect images or spectra of astronomical objects. The spacecraft’s Pointing Control System Two of the three sensors are required to point the relies upon Fine Guidance Sensors to accurately telescope at an astronomical target and then hold measure the position of guide stars and thereby that target steady in a scientific instrument’s field detect and correct unwanted drifts of the telescope of view. These sensors lock onto “guide stars” from its desired pointing. and measure the position of the telescope relative facts to the object being studied. Regular adjustments Launched into Earth orbit in 1990, the Hubble based on these minute measurements keep Space Telescope has three Fine Guidance Sensors Hubble pointed precisely in the right direction. (FGSs). Subsequently, two of the FGSs were replaced by refurbished sensors during servicing The third FGS is available to operate as a missions. The third FGS is the original sensor. scientific instrument. The FGSs are capable of precisely measuring the relative positions of stars, detecting rapid changes in a star’s brightness, and resolving double-star systems that appear as point sources even to Hubble’s cameras. The FGSs can provide star positions that are about 10 times more precise than those observed from a ground-based telescope.
    [Show full text]
  • Hydrogen Subordinate Line Emission at the Epoch of Cosmological Recombination M
    Astronomy Reports, Vol. 47, No. 9, 2003, pp. 709–716. Translated from Astronomicheski˘ı Zhurnal, Vol. 80, No. 9, 2003, pp. 771–779. Original Russian Text Copyright c 2003 by Burgin. Hydrogen Subordinate Line Emission at the Epoch of Cosmological Recombination M. S. Burgin Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, Profsoyuznaya ul. 84/32, Moscow, 117997 Russia Received December 10, 2002; in final form, March 14, 2003 Abstract—The balance equations for the quasi-stationary recombination of hydrogen plasma in a black- body radiation field are solved. The deviations of the excited level populations from equilibrium are computed and the rates of uncompensated line transitions determined. The expressions obtained are stable for computations of arbitrarily small deviations from equilibrium. The average number of photons emitted in hydrogen lines per irreversible recombination is computed for plasma parameters corresponding to the epoch of cosmological recombination. c 2003 MAIK “Nauka/Interperiodica”. 1. INTRODUCTION of this decay is responsible for the appreciable differ- When the cosmological expansion of the Universe ence between the actual degree of ionization and the lowered the temperature sufficiently, the initially ion- value correspondingto the Saha –Boltzmann equi- ized hydrogen recombined. According to [1, 2], an librium. A detailed analysis of processes affectingthe appreciable fraction of the photons emitted at that recombination rate and computations of the temporal time in subordinate lines survive to the present, lead- behavior of the degree of ionization for various sce- ingto the appearance of spectral lines in the cosmic narios for the cosmological expansion are presented background (relict) radiation. Measurements of the in [5, 6].
    [Show full text]
  • The Atmospheric Parameters and Spectral Interpolator for the MILES Stars
    A&A 531, A165 (2011) Astronomy DOI: 10.1051/0004-6361/201116769 & c ESO 2011 Astrophysics The atmospheric parameters and spectral interpolator for the MILES stars Ph. Prugniel1, I. Vauglin1,andM.Koleva2,1 1 Université de Lyon, Université Lyon 1, 69622 Villeurbanne, France; CRAL, Observatoire de Lyon, CNRS UMR 5574, 69561 Saint-Genis Laval, France e-mail: [philippe.prugniel;isabelle.vauglin]@univ-lyon1.fr 2 Instituto de Astrofísica de Canarias, La Laguna, 38200 Tenerife, Spain; Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain e-mail: [email protected] Received 22 February 2011 / Accepted 16 April 2011 ABSTRACT Context. Empirical libraries of stellar spectra are used to classify stars and synthetize stellar populations. MILES is a medium spectral- resolution library in the optical domain covering a wide range of temperatures, surface gravities and metallicities. Aims. We redetermine the atmospheric parameters of these stars in order to improve the homogeneity and accuracy. We build an interpolating function that returns a spectrum as a function of the three atmospheric parameters, and finally we characterize the precision of the wavelength calibration and stability of the spectral resolution. Methods. We used the ULySS program with the ELODIE library as a reference and compared the results with those in the literature. Results. We obtain precisions of 60 K, 0.13, and 0.05 dex, respectively, for Teff ,logg,and[Fe/H] for the FGK stars. For the M stars, the mean errors are 38 K, 0.26, and 0.12 dex and 3.5%, 0.17, and 0.13 dex for the OBA.
    [Show full text]
  • Introduction
    Introduction Onething is certain about this book: by thetimeyou readit, parts of it will be out of date. Thestudy of exoplanets,planets orbitingaround starsother than theSun, is anew andfast-moving field.Important newdiscoveries areannounced on a weekly basis. This is arguablythe most exciting andfastest-growing field in astrophysics.Teamsofastronomersare competing to be thefirsttofind habitable planets likeour ownEarth, andare constantly discovering ahostofunexpected andamazingly detailed characteristics of thenew worlds. Since1995, when the first exoplanet wasdiscoveredorbitingaSun-like star,over 400 of them have been identified.Acomprehensive review of thefield of exoplanets is beyond thescope of this book, so we have chosen to focus on thesubset of exoplanets that are observedtotransittheir hoststar (Figure 1). Figure1 An artist’simpression of thetransitofHD209458 bacrossits star. Thesetransitingplanets areofparamount importancetoour understanding of the formation andevolutionofplanets.During atransit, theapparent brightness of the hoststar drops by afraction that is proportionaltothe area of theplanet: thus we can measure thesizes of transitingplanets,eventhough we cannot seethe planets themselves.Indeed,the transitingexoplanets arethe onlyplanets outside our own Solar System with known sizes.Knowing aplanet’ssize allows its density to be deduced andits bulk compositiontobeinferred.Furthermore, by performing precisespectroscopicmeasurements during andout of transit, theatmospheric compositionofthe planet can be detected.Spectroscopicmeasurements
    [Show full text]